1. Field of the Invention
The present invention relates generally to a mouse for data input and, more specifically, to a third axis input device for a mouse, which combines the parts of a mechanical encoding module and a wheel to form a single module.
2. Description of the Related Art
A conventional mouse comprises an X-axis encoder and a Y-axis encoder for output serial logic signals (for example, 11,10,00,01). Moving the mouse on a flat surface in a specific direction causes relative movement of the data to be processed on the screen of the monitor. Basically, using the mouse to move the position of the data on the screen causes the X-axis encoder and the Y-axis encoder to produce a spot displacement on a plane.
Further, some mice have a third axis input device adapted to control web page scrolling. FIGS. 1–3 show a third axis input device according to the prior art. As illustrated, the third axis input device 60 comprises a hollow wheel holder 61 provided at the bottom board 81 inside the mouse 80, and an encoder module fastened pivotally with the wheel holder 61. The encoder module comprises a plastic wheel 70 with a roller 62 fastened to the hollow center of the plastic wheel 70. The roller 62 has a receiving chamber 63 in one side with a cover shell 67 covering the receiving chamber 63. The cover shell 67 has a retaining flange 68 fastened to the wheel holder 61. A barrel 64 is fixedly mounted in the receiving chamber 63, the barrel 64 having transverse light-guide teeth 65 arranged in parallel around the periphery. A circuit board 66 is fastened to the cover shell 67 and disposed inside the receiving chamber 63, and an infrared transceiver unit 69 is installed in the circuit board 66. The infrared transceiver unit 69 comprises an infrared transmitter 691 adapted to emit infrared light onto the inside wall of the barrel 64. An infrared receiver 692 is adapted to receive infrared light emitted from the infrared transmitter 691 and is guided by the transverse light-guide teeth 65 and to further produce different serial phase signals.
According to the aforesaid third axis input device 60, the barrel 64 is rotated with the roller 62 to encode infrared light into serial phase signals. This design is functional; however, because the third axis input device 60 is comprised of a number of parts, its manufacturing cost is high.
FIG. 4 shows another design of third axis input device for mouse. According to this design, the third axis input device comprises a wheel holder 90 mounted on the bottom board 81 of the mouse 80, a wheel 91 pivoted to the wheel holder 90, and a mechanical encoder module 93 provided at one end of the wheel shaft 92 of the wheel 91. The manufacturing cost of this design of third axis input device is relatively lower than the third axis input device shown in FIGS. 1–3. However, because the wheel 91 and the mechanical encoder module 93 must be separately prepared and installed, this design of third axis input device requires a relatively longer manufacturing time.
Therefore, it is desirable to provide a third axis input device that eliminates the drawbacks of the aforesaid prior art designs.